The nondestructive evaluation of materials for damage and defects often involves the inspection of curved surfaces having limited access, such as engine disk slots, helicopter propulsion components, turbine blades, bolt holes, and automotive components. Typically, the defect appears when the inspection sensor, such as an eddy current sensor, is brought into intimate contact with the surface. For coverage over wide areas of the surface, this inspection requires the use of sensors that are formed into the shape of the curved surface or are fabricated onto a flexible backing that can conform to the shape of the surface.
Compliant substrates, such as foam or ferrite loaded substrates, have been used to enhance the performance of eddy-current sensors and allow sensor arrays to conform to a surface through the compliance of the substrate. These non-rigid substrates offer the advantage of conforming to a wide range of complex shapes, but often require a rigid inner core to maintain the general shape and can result in local variations in pressure on the sensor and a lack of adherence of the array to the surface of the material under test.
The shape of devices and gaps between devices has been controlled by the use of fluids such as water, air and oil for devices such as automobile tires, balloons used in angioplasty to clear arteries in the heart, and in air bearings. Often the desire is to maintain a specific shape without significant compliance after the shape has been established.
In general, the invention addresses the limitations of compressible solid substrates for inspection of confined material surfaces by introducing fluid substrates enclosed in relatively rigid pre-shaped membrane materials or combinations of fluid filled xe2x80x9cballoonsxe2x80x9d with compliant solids, such as foam or elastomers.
In some embodiments a cylindrical shaped balloon is used to press a noncompressible solid shuttle with the approximate shape of the material under test surface (e.g., an engine disk slot) against the material under test surface. Sensors placed on the surface of the shuttle are then used to inspect the material for flaws and defects or to characterize the material properties, such as coating thickness, electrical conductivity, or magnetic permeability.
In other embodiments, a chambered elastic support member, such as a balloon, and means for pressurizing this chamber, are used to locating a sensor near and against the material surface under inspection. For the inspection of electrically conducting materials and magnetic materials, the sensor can be an inductive or eddy current sensor or an eddy current sensor array. In certain embodiments, additional supports can be placed between the sensor and the elastic support. These supports can be rigid or made of an elastic material so that the supports can conform to the shape of the test material surface when the chamber is pressurized. For positioning the elastic support members near the surface of the test material, one embodiment has at least one rigid support element. In other embodiments, a rigid support element forms a core which is then surrounded by a plurality of elastic support members that can conform to the surface of the test material. To enhance the conformability of the sensor against the test material surface, an additional compressible layer, such as a foam, is placed between the support members and the sensor.
In yet other embodiments the sensor is located near the test material surface using both a rigid support member and a chambered elastic support member that can be pressurized. In some embodiments, the rigid support approximates the shape of the test material surface. In another embodiment, an additional compressible layer is placed between the support members and the sensor. In one embodiment, the pressurizable elastic support member is placed behind the sensor to press the sensor against the test material surface. The rigid support can include a rigid body, an actuated portion that can move when the chambered elastic support is pressurized, and a spring for restoring the positions when the pressure is removed. The pressurizable support can be placed between the body and the actuated portion. In another embodiment, the actuated portion presses against an opposing surface of the test material. The actuated portion can have a roller that is in contact with the opposing test material surface and facilitates smooth motion along the surface. In some embodiments, the rigid support forms a core structure that is surrounded by numerous pressurizable supports. In other embodiments, several rigid supports are placed between a pressurizable chamber and a sensor. In yet other embodiments, an additional compressible pad is placed between the rigid supports and the sensor.
Other embodiments have the sensor located near the test material surface using a rigid support member that approximates the shape of the test material surface, a chambered elastic support member than can be pressurized, and a compressible support layer behind the sensor. In some cases the test material surface is substantially concave and is in a partially enclosed region of the component where the ends of the component are used to access the test material surface. In one embodiment, convex tabs are placed on the back of the rigid insert to prevent contact between the insert and the surfaces of the component opposing the test material surface. In certain embodiments, the test material surface is an engine disk slot. In other embodiments, the inspection involves the measurement of surface roughness or surface damage, including fretting.
In yet other embodiments, the sensor is located near the test material surface using a rigid support member that approximates the shape of the test material surface and a chambered elastic support member than can be pressurized. In some embodiments, a flexible ring of a substantially non-expandable material encircles the pressurizable support member, a rigid support and a spring. The ring holds the components in place while the spring helps deflate the pressurizable chamber when the pressure source is removed. The flexible rings and components can be a removable insert for ease of repair when components break. In another embodiment, a second pressurizable elastic member is used to apply the pressure to the first pressurizable elastic material.
In another embodiment, a chambered elastic support member that can be pressurized presses a sensor against the surface of a test material and a support is used to adjust the sensor position. In one embodiment, the support is a rigid pipe that encloses the elastic member except for an opening that is spanned by the sensor. Applying pressure to the elastic member causes it to expand against the sensor and presses the sensor against the test material surface. In another embodiment, the support is a pair of cables that are placed on the sides of the elastic member and held in place by a flexible film. Pressurization of the elastic member causes it to expand against both the surface of the component opposite the test material surface and the sensor. The support can be a rigid rod that allows an operator to translate the sensor over the surface of the test material. Furthermore, an additional rigid support can be placed between the sensor and the elastic member, and a flexible ring of a substantially non-expandable material encircles the pressurizable elastic member, the additional rigid support and the sensor to hold the components in place.